The invention concerns a phase annulus to produce positive phase contrast. Phase contrast microscopy has been known since Zernike. Accomplishment of this process requires production of "phase rings" by vapor-deposition of one or more thin layers on a substrate, which may be of optical glass, for instance. By skillful selection of the layer thickness, the phase of the direct light, which passes through the vapor-deposited phase, can be delayed relative to the phase of the diffracted light, which is the light that does not pass through the phase annulus, by, for instance, .pi./2; or it can be advanced by .pi./2. That latter case is "positive" phase contrast.